The present invention discloses novel steroid mimics wherein a tri- or tetravalent phosphorous atom is isosterically substituted at any one of the seventeen positions occupied by the carbon atom in the steroidal skeleton, and wherein each adjacent position to the phosphorous is either unsubstituted or optionally substituted by nitrogen or an oxygen atom to satisfy the valency of said phosphorous atom. The invention is illustrated schematically below using both aromatic and non-aromatic steroids. Although the isosteric substitution ##STR00001## phosphorous atom in the above structures 3 7 is indicated at 13, 14, and 17 positions, it is to be noted that the phosphorous can be substituted at any one of the seventeen positions in non-aromatic or eleven positions in aromatic steroids. The phosphorous atom may be trivalent or tetravalent, and may be radioactive or non-radioactive. The adjacent atoms, X, Y, or Z may be carbon, oxygen, or nitrogen. Other positions in the steroid mimics 3 8 may be optionally substituted alkyl, aryl, or other polar or non-polar functional groups to optimize biodistribution, receptor binding, and pharmacokinetic properties.